FIG. 1 is a schematic view illustrating laminated structure of a top-emission organic light emitting device including a reflection electrode serving as an anode.
FIG. 1 illustrates a reflection electrode 1 for reflecting light, which is generated on a substrate, a hole transport layer 2, an emission layer 3 including a red light emission layer 3R, a green light emission layer 3G and a blue light emission layer 3B, an electron transport layer 4, an electron injection layer 5 and a light extraction electrode 6 for transmitting light.
It is known that the organic light emitting device described above has the maximal value of light emitting efficiency when an optical distance from an emission interface of the emission layer 3 of FIG. 1 to the reflection electrode 1 of FIG. 1 is set to odd multiples of ¼ emission wavelength λ (Japanese Patent Application Laid-Open No. 2000-243573).
In order to improve the light emitting efficiency by using the phenomenon described above, there is used a multicolor display apparatus including charge transport layers having different thicknesses for each color (Japanese Patent Application Laid-Open No. 2000-323277).
In addition, there is also known a multicolor display apparatus in which charge transport property of the emission layer is changed for each color without changing thicknesses of organic layers having different colors, and then chromaticity of red, green and blue is adjusted (Japanese Patent Application Laid-Open No. 2004-134101). More specifically, the charge transport property of the emission layer of a red light emitting device (R device) is made to be hole transport property, and the charge transport property of the emission layers of a green light emitting device (G device) and a blue light emitting device (B device) are each made to be electron transport property. In the R device having a long wavelength, the emission layer is used as a layer for causing an optical path difference. In the G device and the B device having a short wavelength, the emission layers are not used as layers for causing the optical path difference, thereby adjusting the chromaticity for each color.
In the multicolor display apparatus described in Japanese Patent Application Laid-Open No. 2000-323277, for the purpose of improving light extraction efficiency by an interference effect, the optical distance of the charge transport layer is attempted to be set based on the emission wavelength.
However, in order to set the optical distance of the charge transport layer based on the emission wavelength, it is necessary to separately apply colors on the charge transport layer with the use of a technique such as a mask vapor deposition, the charge transport layer being originally unnecessary to be separately applied with colors in only the consideration of charge transport. Therefore, there have been problems such as cost increase and an elongated time for manufacturing by using the mask vapor deposition for layers other than the emission layer.
Further, in the multicolor display apparatus described in Japanese Patent Application Laid-Open No. 2004-134101, the thickness of the charge transport layer is not changed for each color, but there is a room in which the three-color devices of R device, G device and B device can be brought close to more optimum constructive interference.